1. Field of the Invention PA1 first printing-mode executing means for performing printing by ejecting at least cyan, magenta, yellow and black inks from the printing head; PA1 second printing mode executing means for performing printing by ejecting at least cyan, magenta, and yellow inks, and cyan and magenta inks respectively having lower densities than that of the cyan and magenta inks; and PA1 printing control means for making one of the first and second printing-mode executing means perform printing. PA1 setting one of a first printing mode performing printing by ejecting at least cyan, magenta, yellow, and black inks from the printing head and a second printing mode performing printing by ejecting at least cyan, magenta, and yellow inks, and cyan and magenta inks having a lower density than that of the cyan and magenta inks from the printing head, as a printing mode; and PA1 performing printing in the printing mode set by the step for setting.
The present invention relates generally to an ink-jet printing apparatus and an ink-jet printing method performing printing by ejecting ink on a printing medium. More specifically, the invention relates to an ink-jet printing apparatus and an ink-jet printing method performing printing using ink, a liquid which can make a coloring agent in the ink insoluble or coagulated, or a plurality of inks having different densities. It should be noted that the present invention is applicable of all devices using printing media, such as paper, cloth, a non-woven fabric, an OHP sheet and so on, and more particularly to a business machine, such as a printer, a copy machine, a facsimile machine and the like, and manufacturing industrial machines, such as a textile printing apparatus and so on, as applicable apparatus.
2. Description of the Prior Art
Conventionally, an ink-jet printing apparatus performing printing for a printing medium, such as paper, cloth, a plastic sheet, an OHP sheet or the like (hereinafter simply referred to as printing paper) has various advantages, such as the capability of high-density and high-speed printing, and so on, and is widely employed as output means of an information processing system, such as a copy machine, a facsimile machine, an electronic typewriter, a wordprocessor, a printer as an output terminal of workstation and the like, or a handy printer or a portable printer to be provided in a personal computer, a host computer, an optical disk device, a video apparatus and so on.
In this case, an ink-jet printing apparatus has a construction adapted to a function, a mode of use and so on specific to each of these devices, respectively. Typically, the ink-jet printing apparatus includes a carriage mounting a printing head as printing means and an ink tank, transporting means for transporting the printing paper, and control means for controlling these components. The printing head which ejects ink droplets through a plurality of ejection openings, is scanned with respect to a printing paper in a direction (primary scanning direction) perpendicular to a transporting direction (auxiliary scanning direction) to perform ink ejection while scanning in the primary scanning direction. Also, the printing paper is intermittently transported in an amount corresponding to a printing width between each two scannings. This construction, in which printing is performed by ejecting ink on the printing paper, has been widely used as a printing system with a low running cost and low noise associating with printing. Further, by employing a printing head in which a large number of ejection openings for ejecting ink are arranged in alignment in the auxiliary scanning direction and by scanning the printing head on the printing paper, printing in a width corresponding to the number of ejection openings can be performed. By this arrangement, speeding up of the printing operation can be achieved.
In addition, in recent years, depending upon demand for full-color printing, there has been practiced an apparatus which mounts printing heads for three or four color inks, and is capable of forming a full color image. Such an apparatus mounts three or four kinds of printing heads and ink tanks for three primary colors of yellow (Y), magenta (M) and cyan (C) or four colors including black (hereinafter occasionally referred to as Bk) in addition to three primary colors.
In color printing by the conventional ink-jet printing system, it is generally known that the goals of preventing bleeding of the ink, and increasing the density of a black image and preventing feathering are inconsistent with each other. Therefore, in the conventional apparatus, it has been difficult to sufficiently satisfy the user's needs for quality of a color printing image. It has been known that this has been caused for following reasons.
Normally, in the case of performing color printing on a plane paper by an ink-jet printing method, bleeding of the ink in a boundary of respective color regions forming an image can be prevented by using an ink having a relatively high penetration speed, thus having high fixing ability. However, when using ink having high penetration speed, it is often the case that the density of the black image portion becomes low, and color development ability in color image portions other than black also becomes low. Furthermore, upon printing of a line image, typically represented by character or the like, it is possible to cause penetration of ink along fibers of the paper, thereby causing so-called feathering. In particular, in comparison with the image printed by a color other than black, feathering in the character printed by black ink is easily perceived to make the character vague for lack of sharpness. As set forth, as a result of the attempt to prevent bleeding between respective colors of inks, the quality of the overall printed image can be significantly lowered.
In contrast to this, it can be considered that the high density or the like of the image is realized while preventing feathering, by ejecting a large amount of the ink having relatively low penetration ability to the plane of the paper. However, in such case, for example, in the portions located adjacent the boundary of the black image and the color image, bleeding of the black ink and the color inks can be caused, to significantly lower the quality of the printed image.
As one system providing a solution for the foregoing problem, a system is known in which a heater is provided in a printing apparatus to promote evaporation of the ink and can obtain a color image having high-color-developing ability with no bleeding between the colors. However, such system may cause the apparatus to be bulky and have a high cost.
In Japanese Patent Application Laid-open No. 146,355/1991, there has been proposed a system in which printing is not performed for respective regions along the boundary between regions of the black and the color. However, this method requires varying the data for printing and thus it may happen that the quality of the image to be actually printed is degraded.
Also, in Japanese Patent Application Laid-open No. 158,049/1992, there is proposed a method of printing, in which printing heads corresponding to a plurality of colors for color printing and a printing head for character printing are provided, and printing is performed by switching use of the printing head for the color image and the printing head for character printing. In this method, when the black image printed by the color printing head and the black image printed by the character printing head are present in an admixing manner, an uncomfortable feeling may be caused due to a difference between the respective printing quality of the two modes.
Furthermore, there has been considered a method of preventing bleeding between the black ink and the color inks at the boundary between the black image and other color image by overlaying color inks in a black region along the boundary between the black and color images. As set forth above, the black can be obtained by overlaying three colors, Y, M, C (admixing of the colors). However, the black image obtained by overlaying the color inks tends to have a lower color-development ability in comparison with the normal black ink.
On the other hand, in Japanese Patent Application Laid-open No. 084,992/1981 and Japanese Patent Application Laid-open No. 063,185/1989, a technology employing a liquid which makes a dye in the ink insoluble is disclosed.
Japanese Patent Application Laid-open No. 084,992/1981, discloses a method, in which a material for fixing the dye is preliminarily applied on the printing paper. However, this method requires a special printing paper. Also, in order to preliminarily apply the material for fixing the dye, it is inherent to increase the size and a cost of the apparatus. Furthermore, it is relatively difficult to stably apply a predetermined layer thickness of the material on the printing paper.
Further, in Japanese Patent Application Laid-open No. 063,185/1989, there is disclosed a technology, in which a transparent ink, which makes dye insoluble, is deposited on the printing paper by means of an ink-jet printing head. By this method, since the dot diameter of the transparent ink is set greater than the dot diameter of the image printing ink, desired characteristics can be satisfied even when the deposition positions of the image printing ink and the transparent ink are shifted relative to each other. However, in this method, since the amount of the transparent ink to be deposited on the position corresponding to the image position is greater than that required, a longer fixing period becomes necessary and the image can be unclear.
Furthermore, in Japanese Patent Application Laid-open No. 195,823/1995, by applying a transparent precursor substance on a surface of the printing medium in advance of ink-jet printing, it enables color printing to be performed by one scan.
As set forth above, while the foregoing method disclosed in respective publications concerning the liquid which makes the dye insoluble, holds no critical drawbacks, respectively, it may be possible to prevent bleeding of ink between respective colors when the liquid making the dye in the ink insoluble is applied for color printing.
The commonly owned Japanese Patent Application Laid-open No. 039,795/1996 proposes an ink-jet printing method, which uses a liquid making the dye insoluble and solves the respective drawbacks set forth above, and can realize a low-running cost with restricting consumption of the liquid making the dye insoluble, to provide superior water resistance for the image on the plain paper than that in prior art, to make it possible to obtain a high-density image, and to make it possible to obtain an image achieving high color development without causing bleeding between colors.
In addition to solving of the problem of the bleeding of inks, the foregoing system further realizes both a higher image quality and higher printing speed in a case where a color image is printed on plain paper by the ink-jet printing system.
More specifically, associated with the improvement and spreading of the computer environment and multi-media, is a demand for a higher quality of color image which is becoming progressively stronger and a demand for diversification of image information to be handled therein. Adapting for such demand, there has been practiced a printer which additionally employs color inks having lower dye concentration than that of the normal color ink to be used for color printing to enable the output of a color image of comparable quality to a silver film photograph.
For example, the method for printing of a color image employing six kinds of inks, in which additional cyan ink and magenta ink, respectively, having lower dye concentration than that of the normal cyan and magenta inks, are employed in addition to four kinds of inks of black ink, cyan ink, magenta ink and yellow ink to be used in normal color image printing, has been known.
However, in the foregoing method, while high image quality comparable with the silver film photograph can be realized, a problem can be encountered in that, for certain types of users who mainly output black image primarily consisting of characters, as are frequently output in an office environment or for users who mainly output business documents, in which color graphics are admixed in the black image, the printing heads for ejecting the inks of low dye concentration are wasted since they are rarely used.